A. Field of the Invention
The present invention relates generally to nucleic acid sequences useful as probes for the diagnosis of cancer and methods relating thereto. More particularly, the present invention concerns probes and methods useful in diagnosing, identifying and monitoring the progression of diseases of the prostate through measurements of gene products.
B. Description of the Related Art
Carcinoma of the prostate (PCA) is the second-most frequent cause of cancer related death in men in the United States (Boring, 1993). The increased incidence of prostate cancer during the last decade has established prostate cancer as the most prevalent of all cancers (Carter and Coffey, 1990). Although prostate cancer is the most common cancer found in United States men, (approximately 200,000 newly diagnosed cases/year), the molecular changes underlying its genesis and progression remain poorly understood (Boring et al., 1993). According to American Cancer Society estimates, the number of deaths from PCA is increasing in excess of 8% annually.
An unusual challenge presented by prostate cancer is that most prostate tumors do not represent life threatening conditions. Evidence from autopsies indicate that 11 million American men have prostate cancer (Dbom, 1983). These figures are consistent with prostate carcinoma having a protracted natural history in which relatively few tumors progress to clinical significance during the lifetime of the patient. If the cancer is well-differentiated, organ-confined and focal when detected, treatment does not extend the life expectancy of older patients.
Unfortunately, the relatively few prostate carcinomas that are progressive in nature are likely to have already metastasized by the time of clinical detection. Survival rates for individuals with metastatic prostate cancer are quite low. Between these two extremes are patients with prostate tumors that will metastasize but have not yet done so. For these patients, surgical removal of their prostates is curative and extends their life expectancy. Therefore, determination of which group a newly diagnosed patient falls within is critical in determining optimal treatment and patient survival.
Although clinical and pathologic stage and histological grading systems (e.g., Gleason's) have been used to indicate prognosis for groups of patients based on the degree of tumor differentiation or the type of glandular pattern (Carter and Coffey, 1989; Diamond et al., 1982), these systems do not predict the progression rate of the cancer. While the use of computer-system image analysis of histologic sections of primary lesions for "nuclear roundness" has been suggested as an aide in the management of individual patients (Diamond et al., 1982), this method is of limited use in studying the progression of the disease.
Recent studies have identified several recurring genetic changes in prostate cancer including: 1) allelic loss (particularly loss of chromosome 8p and 16q) (Bova, et al., 1993; Macoska et al., 1994; Carter et al., 1990); 2) generalized DNA hypermethylation (Isaacs et al., 1994); 3) point mutations or deletions of the retinoblastoma (Rb) and p53 genes (Bookstein et al., 1990a; Bookstein et al., 1990b; Isaacs et al., 1991); 4) alterations in the level of certain cell-cell adhesion molecules (i.e., E-cadherin/alpha-catenin) (Carter et al., 1990; Morton et al., 1993; Umbas et al., 1992) and aneuploidy and aneusomy of chromosomes detected by fluorescence in situ hybridization (FISH), particularly chromosomes 7 and 8 Macoska et al., 1994; Visakorpi et al., 1994; Takahashi et al., 1994; Alcaraz et al., 1994).
The analysis of DNA content/ploidy using flow cytometry and FISH has been demonstrated to have utility predicting prostate cancer aggressiveness (Pearsons et al., 1993; Macoska et al., 1994; Visakorpi et al., 1994; Takahashi et al., 1994; Alcaraz et al., 1994; Pearsons et al., 1993), but these methods are expensive, time-consuming, and the latter methodology requires the construction of centromere-specific probes for analysis.
Specific nuclear matrix proteins have been reported to be associated with prostate cancer. (Partin et al., 1993). However, these protein markers apparently do not distinguish between benign prostate hyperplasia and prostate cancer. Martin et al., 1993). Unfortunately, markers which cannot distinguish between benign and malignant prostate tumors are of little value.
It is known that the processes of transformation and tumor progression are associated with changes in the levels of messenger RNA species (Slamon et al., 1984; Sager et al., 1993; Mok et al., 1994; Watson et al., 1994). Recently, a variation on PCR analysis known as RNA fingerprinting has been used to identify messages differentially expressed in ovarian or breast carcinomas (Liang et al., 1992; Sager et al., 1993; Mok et al., 1994; Watson et al., 1994). By using arbitrary primers to generate "fingerprints" from total cell RNA, followed by separation of the amplified fragments by high resolution gel electrophoresis, it is possible to identity RNA species that are either up-regulated or down-regulated in cancer cells. Results of these studies indicated the presence of several markers of potential utility for diagnosis of breast or ovarian cancer, including a6-integrin (Sager et al., 1993), DEST001 and DEST002 (Watson et al., 1994), and LF4.0 (Mok et al., 1994).
There remain, however, deficiencies in the prior art with respect to the identification of the genes linked with the progression of prostate cancer and the development of diagnostic methods to monitor disease progression. Likewise, the identification of genes which are differentially expressed in prostate cancer would be of considerable importance in the development of a rapid, inexpensive method to diagnose prostate cancer.